The design and development of load-bearing structures often includes the structural testing of components and materials that will be used in such structures. Structural testing provides mechanical property data such as the strength and failure mode of tested components and materials under different environmental conditions such as temperature and relative humidity. The mechanical property data may be used in the design and analysis of a structure such that the structure performs as intended when operating in its service environment.
Compression testing is a type of structural test wherein a compressive test load is applied to a test specimen. The test specimen may be provided as a rectangularly-shaped test panel or test coupon of a predetermined size. The test panel may be formed of composite material (i.e., fiber-reinforced polymer matrix material) and/or metallic material. The test panel may be loaded into a testing machine such that a lower panel edge of the test panel is supported on a base assembly of a test fixture which, in turn, may be supported on a lower platen of the testing machine. A load transmitting interface may be mounted over an upper panel edge of the test panel. The testing machine may include a vertically-movable load head located above the load transmitting interface. The load head may include an upper platen that may be moved downwardly into bearing contact with the load transmitting interface such that a compressive test load may be axially applied to the test panel along a lengthwise (i.e., vertical) direction of the test panel.
For accuracy of testing, the compressive test load is preferably uniformly-distributed across the upper and lower panel edge. However, a test panel may occasionally be provided in a slightly-irregular shape wherein the edges of the test panel are non-perpendicular to one another, or wherein the upper and lower panel edges are non-parallel to one another and resulting in one end of the upper panel edge being higher than an opposite end of the upper panel edge. As a result, the upper platen may initially apply the compressive test load on the higher end of the upper panel edge and the lower end of the test panel may initially be unloaded, resulting in eccentric loading of only one of the opposing ends of the upper panel edge instead of uniformly distributing the compressive test load across the upper panel edge. The non-uniform distribution of the compressive test load may result in premature failure of the test panel and invalid test data.
In conventional practice, the alignment of the test panel may be checked and adjusted by visually searching for light gaps between the load transmitting interface and the upper platen, measuring the width of the gaps using an assortment of feeler gauges, fabricating shims according to the gap measurements, and then installing the shims between the base assembly and the lower platen. The test setup may then be checked for gaps and the process of locating and measuring gaps, fabricating shims, and installing the shims may be repeated in a trial-and-error manner until the gaps between the load transmitting interface and the upper platen are substantially eliminated. Unfortunately, the process of locating and measuring gaps followed by fabricating and installing shims and rechecking for gaps is a time-consuming and labor-intensive process which significantly increases the overall time and expense of structural testing.
As can be seen, there exists a need in the art for a system and method for determining and adjusting the orientation of a test panel in a testing machine and which avoids the time and expensive associated with the conventional trial-and-error process of locating and measuring gaps and installing and fabricating shims.